| 1. |
- Choularton, T. W., et al.
(författare)
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The Great Dun Fell Cloud Experiment 1993 : An overview
- 1997
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Ingår i: Atmospheric Environment. - 1352-2310. ; 31:16, s. 2393-2405
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Tidskriftsartikel (refereegranskat)abstract
- The 1993 Ground-based Cloud Experiment on Great Dun Fell used a wide range of measurements of trace gases, aerosol particles and cloud droplets at five sites to study their sources and sinks especially those in cloud. These measurements have been interpreted using a variety of models. The conclusions add to our knowledge of air pollution, acidification of the atmosphere and the ground, eutrophication and climate change. The experiment is designed to use the hill cap cloud as a flow-through reactor, and was conducted in varying levels of pollution typical of much of the rural temperate continental northern hemisphere in spring-time.
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| 2. |
- Bower, K. N., et al.
(författare)
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The Great Dun Fell experiment 1995 : An overview
- 1999
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Ingår i: Atmospheric Research. - 0169-8095. ; 50:3-4, s. 151-184
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Tidskriftsartikel (refereegranskat)abstract
- During March and April of 1995 a major international field project was conducted at the UMIST field station site on Great Dun Fell in Cumbria, Northern England. The hill cap cloud which frequently envelopes this site was used as a natural flow through reactor to examine the sensitivity of the cloud microphysics to the aerosol entering the cloud and also to investigate the effects of the cloud in changing the aerosol size distribution, chemical composition and associated optical properties. To investigate these processes, detailed measurements of the cloud water chemistry (including the chemistry of sulphur compounds, organic and inorganic oxidised nitrogen and ammonia), cloud microphysics and properties of the aerosol and trace gas concentrations upwind and downwind of the cap cloud were undertaken. It was found that the cloud droplet number was generally strongly correlated to aerosol number concentration, with up to 2000 activated droplets cm-3 being observed in the most polluted conditions. In such conditions it was inferred that hygroscopic organic compounds were important in the activation process. Often, the size distribution of the aerosol was substantially modified by the cloud processing, largely due to the aqueous phase oxidation of S(IV) to sulphate by hydrogen peroxide, but also through the uptake and fixing of gas phase nitric acid as nitrate, increasing the calculated optical scattering of the aerosol substantially (by up to 24%). New particle formation was also observed in the ultrafine aerosol mode (at about 5 nm) downwind of the cap cloud, particularly in conditions of low total aerosol surface area and in the presence of ammonia and HCl gases. This was seen to occur at night as well as during the day via a mechanism which is not yet understood. The implications of these results for parameterising aerosol growth in Global Climate Models are explored.
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| 3. |
- Kuiper, Pieter, 1960-, et al.
(författare)
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Resonant X-Ray raman spectra of Cu dd excitations in Sr2CuO2Cl2
- 1998
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Ingår i: Physical Review Letters. - College Park, MD : American Physical Society. - 0031-9007 .- 1079-7114. ; 80:23, s. 5204-5207
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Tidskriftsartikel (refereegranskat)abstract
- We present resonant x-ray Raman scattering results on Sr2CuO2Cl2, a model compound for high- Tc superconductors. We demonstrate that the dd excitations can be observed and show that the polarization dependence can be used to identify the dd excitations. We find the transition from the dx2−y2 ground state to the dxy excited state at 1.35 eV and to the degenerate dxz and dyz excited states at 1.7 eV. From analysis of the polarization dependence we conclude that the d3z2−r2 orbital energy is at 1.5 eV and not in the midinfrared (0.5 eV) as recently suggested. We use recent theoretical arguments to show that the d3z2−r2 excitation is accompanied by a local spin flip resulting in a shift upwards of 0.2 eV due to the exchange interaction with the neighboring spins. ©1998 American Physical Society.
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| 4. |
- Andersson, S, et al.
(författare)
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CO dissociation characteristics on size-distributed rhodium islands on alumina model substrates
- 1998
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Ingår i: JOURNAL OF CHEMICAL PHYSICS. - : AMER INST PHYSICS. - 0021-9606. ; 108:7, s. 2967-2974
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- The dissociation of CO on size-distributed Rh particles supported on a thin alumina film has been studied with high resolution X-ray Photoelectron Spectroscopy (XPS) and X-ray Absorption Spectroscopy (XAS). Adsorbed CO dissociates upon heating to temperat
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| 5. |
- Andersson, S, et al.
(författare)
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Metal-oxide interaction for metal clusters on a metal-supported thin alumina film
- 1999
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Ingår i: SURFACE SCIENCE. - : ELSEVIER SCIENCE BV. ; 442:1
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- The interaction between deposited metal clusters and a thin model alumina film grown on NiAl(110) have been studied using X-ray absorption spectroscopy (XAS) and core and valence photoelectron spectroscopy. A lower limit for the fundamental gap of the sup
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| 6. |
- Andersson, S, et al.
(författare)
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Temperature dependent XPS study of CO dissociation on small Rh particles
- 1998
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Ingår i: VACUUM. - : PERGAMON-ELSEVIER SCIENCE LTD. - 0042-207X. ; 49:3, s. 167-170
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- We have used temperature dependent X-ray Photoelectron Spectroscopy (XPS) to study the heating-induced CO dissociation on oxide-supported Rh particles through observation of changes undergone by the adsorbate CO and the formation of atomic carbon from the
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| 7. |
- Arbiser, JL, et al.
(författare)
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Oncogenic H-ras stimulates tumor angiogenesis by two distinct pathways
- 1997
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424. ; 94:3, s. 861-866
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Tidskriftsartikel (refereegranskat)abstract
- The switch from a quiescent tumor to an invasive tumor is accompanied by the acquisition of angiogenic properties. This phenotypic change likely requires a change in the balance of angiogenic stimulators and angiogenic inhibitors. The nature of the angiogenic switch is not known. Here, we show that introduction of activated H-ras into immortalized endothelial cells is capable of activating the angiogenic switch. Angiogenic switching is accompanied by up-regulation of vascular endothelial growth factor and matrix metalloproteinase (MMP) bioactivity and down-regulation of tissue inhibitor of MMP. Furthermore, we show that inhibition of phosphatidylinositol-3-kinase leads to partial inhibition of tumor angiogenesis, thus demonstrating that activated H-ras activates tumor angiogenesis through two distinct pathways. Finally, we show evidence for two forms of tumor dormancy.
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| 8. |
- Frank, M, et al.
(författare)
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Particle size dependent CO dissociation on alumina-supported Rh: a model study
- 1997
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Ingår i: CHEMICAL PHYSICS LETTERS. - : ELSEVIER SCIENCE BV. - 0009-2614. ; 279:1-2, s. 92-99
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Via deposition of Ph from the gas phase onto a thin, well-ordered alumina film we have prepared various of alumina-supported Rh particle systems. The morphologies and particle sizes have been characterised with spot profile analysis LEED and STM measureme
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| 9. |
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| 10. |
- Libuda, J, et al.
(författare)
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Interaction of rhodium with hydroxylated alumina model substrates
- 1997
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Ingår i: SURFACE SCIENCE. - : ELSEVIER SCIENCE BV. - 0039-6028. ; 384:1-3, s. 106-119
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- In order to investigate how metal growth and metal-oxide interaction depend on the chemical properties of oxide surfaces, we describe a modification procedure which allows the introduction of surface hydroxyl groups on a well-ordered Al2O3 film on NiAl(II
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